Smooth endoplasmic reticulum cluster presence does not affect embryo ploidy

PURPOSE

We examined the impacts of the smooth endoplasmic reticulum cluster (sERC) presence on embryonic development and blastocyst ploidy.

METHODS

Patients who underwent oocyte retrieval from January 2019 to November 2021 were included in the study. We classified the oocytes into three groups: normal oocytes in the sERC ( -) cycle, normal oocytes in the sERC ( +) cycle, and sERC ( +) oocytes. Next, the levels of serum estradiol, progesterone, anti-Mullerian hormone, follicle-stimulating hormone, and human menopausal gonadotropin were compared between the groups. Moreover, fertilization, degeneration, and abnormal fertilization rates were compared between groups. To investigate developmental outcomes, the blastocyst and good-quality blastocyst rates after intracytoplasmic sperm injection were compared. The quality of the transferred blastocysts was evaluated at follow-up. Additionally, embryos were submitted for next-generation sequencing analysis to examine the effect of sERC presence on ploidy.

RESULTS

The sERC ( +) group had significantly higher serum estradiol, serum progesterone, and serum anti-Mullerian hormone concentrations compared to those in the sERC ( -) group (P < 0.01). The abnormal fertilization rate was higher in the sERC ( +) cycle-sERC ( +) oocyte group (16.1%; 37/230) than in the sERC ( +) cycle-normal oocyte (6.2%; 63/971) and sERC ( -) cycle-normal oocyte groups (7.1%; 174/2467) (P < 0.01). After embryo transfer, nine women gave birth, and no confirmed congenital anomalies were observed. There was no significant difference in ploidy between the sERC ( +) and sERC ( -) groups.

CONCLUSION

The occurrence rates of embryos with euploidy were similar between the sERC ( +) and sERC ( -) groups.

A higher incidence of cleavage failure in oocytes containing smooth endoplasmic reticulum clusters

PURPOSE

In human oocytes, sERCs are one of the dysmorphic phenotypes that have been reported. Significantly reduced pregnancy rates and a comparatively higher number of abnormities in live births appear to be associated with the presence of sERCs in oocytes. However, some reports have shown that healthy babies can be born, without any reduced pregnancy rates, from oocytes observed to contain sERCs. Thus, the clinical and scientific significance of oocytes that harbor sERCs remains controversial.

METHODS

The presence of sERCs was evaluated using a time-lapse system while studying the dynamic changes within oocytes and embryos. Logistic regression analysis was carried out to explore the independent variables for meiotic and mitotic cleavage failure..

RESULTS

The incidence of mitotic cleavage failure and the incidence of meiotic cleavage failure during the second polar body extrusion in oocytes with sERCs were found to be significantly higher than that in oocytes without sERCs. Furthermore, ICSI was found to have a greater frequency of meiotic failure than IVF.

CONCLUSIONS

In cases of cleavage failure, an embryonic cell could become tetraploid and may induce abnormal chromosomal configurations. Some cells exposed to cleavage failure may become trophectoderm cells and form placental abnormalities. Even if they develop into trophectoderm cells, the ICM can be susceptible to further cleavage failure and may in turn cause further aneuploidy. For these reasons, it is important to monitor pregnancies and births derived from oocytes that contained sERCs.